PROCEDE PERMETTANT D'APPAUVRIR LA TENEUR EN BROMURE D'UNE SOLUTION AQUEUSE CONTENANT DU BROMURE A L'AIDE D'EAU OXYGENEE

METHOD FOR REDUCING THE BROMIDE CONTENT IN AN AQUEOUS BROMIDE-CONTAINING SOLUTION USING HYDROGEN PEROXIDE

Abrégé français

L'invention concerne un procédé permettant d'appauvrir le bromure contenu dans une solution à l'aide d'eau oxygénée.

Abrégé anglais

The invention relates to a method for reducing the bromide content in an
aqueous bromide-containing solution using hydrogen peroxide.

Revendications

- 8 -
claims
1. A method for preparing magnesium chloride having a
bromide content of less than 500 ppm,
characterized in that bromide depletion, hydrogen
peroxide is added to a solution comprising the
magnesium chloride.
2. The method as claimed in claim 1, characterized in
that the solution is an aqueous solution.
3. The method as claimed in claim 1 or 2,
characterized in that the solution from which
bromide is depleted, has a pH of ~ 5.
4. The method as claimed in one of claims 1 to 3,
characterized in that magnesium chloride having a
bromide content of less than 25 ppm is prepared.
5. The method as claimed in one of claims 1 to 4,
characterized in that, in addition to bromide,
bromate is depleted from the solution.

Description

CA 02336698 2001-O1-04
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Method for reducing the bromide content of an aqueous
bromide-containing solution using hydrogen peroxide
The present invention relates to a process for reducing
the bromide content of a solution using hydrogen
peroxide. The present invention also relates to a
method in which, in addition to the bromide content,
the bromate content is also reduced.
In many fields of application, for example chemistry or
pharmacy, the maximum bromide content of chemical
compounds used is a problem. Maintaining maximum limits
of bromide concentration is of importance, inter alia,
in the pharmaceutical industry.
When bromide-containing chemicals are used in the
pharmaceutical sector, the purity requirements are
based on the corresponding pharmacopoeias (Pharma Euro
III, pp. 1234-1235). Compounds which are of importance
in this connection are, for example, alkali metal
compounds and alkaline earth metal compounds.
Especially in the case of alkali metal compounds and
alkaline earth metal compounds of natural origin, the
bromide content is an important problem, since numerous
anions of, for example, alkali metal salts and alkaline
earth metal salts are associated with bromide. For
example, this applies to naturally occurring alkali
metal chlorides and alkaline earth metal chlorides.
For magnesium chloride, the European Pharmacopoeia, for
example, has required since January 1, 1997, a limiting
value for bromide content of 500 ppm.
A method for reducing the bromide content by which such
a total bromine content of a compound may be achieved
is, for example, the introduction of gaseous chlorine
into a solution of the corresponding compound in a
suitable solvent, for example water.

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DE-A 21 18 623 discloses, for example, a method for
purifying aqueous magnesium chloride solutions in which
the bromide content is reduced by introducing chlorine
gas into these solutions.
DE-A 26 13 28 describes a method for preparing highly
concentrated magnesium chloride solutions. The
debromination described in this publication takes place
hot using gaseous chlorine.
However, handling gaseous chlorine, owing to the
reactivity of this gas, represents a high hazard
potential. Therefore, the corresponding methods and
experimental setups, for safety reasons, generally have
high equipment requirements and thus also high
financial outlay.
An object of the present inventions was therefore to
provide an industrial method which is simple to carry
out in terms of apparatus and in which bromide can be
reduced in solutions.
This object has been achieved by using hydrogen
peroxide as oxidizing agent for bromide. Accordingly,
the present invention relates to a method for reducing
the bromide content of a solution using hydrogen
peroxide.
The most important compounds whose solutions are
treated by the inventive method to reduce the bromide
content include alkali metal compounds and alkaline
earth metal compounds.
The present invention therefore also relates to a
method which is characterized in that the aqueous
solution is a solution of alkali metal compounds and/or
alkaline earth metal compounds.

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In particular, the present invention relates to a
method which is characterized in that the alkali metal
compounds and alkaline earth metal compounds are alkali
metal chlorides and alkaline earth metal chlorides.
Generally, in the inventive method, it is not critical
at what concentration hydrogen peroxide is used. In
particular, it is possible to adapt this concentration
to the requirements of the purification. Those which
may be mentioned are, for example, the contamination of
the solution, that is to say its bromide content or its
content of other impurities which can be oxidized by
hydrogen peroxide.
The pH of the solution whose bromide content is to be
reduced is generally in the inventive method in the
range < 7, preferably in the range S 6, and
particularly preferably in the range S 5.
The present invention therefore relates to a method as
described above which is characterized in that the
aqueous solution has a pH of S 5 during the reduction.
The pH of the solution is set in the inventive method
to the desired value via acids or bases, depending on
the initial pH of the solution.
Generally, the addition of acids is necessary in order
to bring the pH to the desired values as described
above Acids which are preferably used are inorganic
acids. Particular preference is given here to
hydrochloric acid.
Obviously, it is possible within the context of the
inventive method to add the acid, if necessary, in the
gaseous state to the solution. However, preference is
given to addition of the acid in solution.

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The required amount of acid can be adapted here to
operational requirements of the experiment. It is only
necessary to ensure that, after adding the acid and
hydrogen peroxide, the pH of the solution is in the
desired range, as described above.
Preferably, the content of free acid of the solution to
be depleted is in the range from O.G1 to 25o by weight,
particularly-preferably in the range from 0.1 to loo by
weight, and in particular in the range from 0.3 to 50
by weight.
The sequence of addition of acid and hydrogen peroxide
is generally not critical here. It is conceivable, for
example, that firstly acid is added to the solution to
be depleted and subsequently thereto hydrogen peroxide.
The reverse sequence is also possible.
The bromine formed by oxidation in the course of the
method can, in the inventive method, be removed from
the solution by all methods known from the prior art.
In particular, the removal process can be performed by
boiling or stripping the solution. It is also
conceivable to apply a vacuum to the solution.
Obviously, it is also conceivable to combine suitable
methods. Thus, it is possible, for example, to heat the
solution and at the same time to apply a vacuum.
Therefore, the present invention also relates to
method as described above which is characterized in
that the bromine formed during the depletion is removed
from the solution by boiling the solution, stripping
the solution and/or by applying a. vacuum to the
solution.
If bromine is removed from the so~ution solely by
stripping, air is injected into the solution at a

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throughput of generally from 1 to 100, preferably from
2 to 50, particularly preferably from 3 to 20, 1/min.
Regardless of the method which is used in the removal
process, in the inventive method, after the depletion,
bromide contents are found which are < 500 ppm,
preferably < 300 ppm, particularly preferably
< 100 ppm, further particularly preferably < 50 ppm, in
particular w25 ppm.
The present invention therefore also relates to a
method as described above which is characterized in
that the bromide content of the depleted solution is
less than 25 ppm.
A further advantage of the inventive method is based on
the fact that simultaneously with bromide bromate,
where present, can also be removed from the solution.
The present invention therefore also relates to a
method as described above which is characterized in
that, in addition to the bromide content, the bromate
content of the solution is reduced.
Hydrogen peroxide is particularly useful here when the
25- bromate content of the solution is higher than its
bromide content.
In its most general form the invention relates to the
use of hydrogen peroxide for reducing the bromide
content of a bromide-containing aqueous solution.
The present invention further relates to the use of
hydrogen peroxide for reducing the bromate content of
bromide- and bromate-containing aqueous solutions.
The present invention also relates to the use of
hydrogen peroxide for removing bromide or bromate or a
mixture of bromide and bromate from an aqueous solution
that is used in the production of medicaments.

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The present invention also relates to the use of high-
purity magnesium chloride for hemodialysis,
hemofiltration or peritoneal dialysis solutions and
parenteral applications, in particular infusion
solutions, which can be prepared by crystallization of
a magnesium chloride solution, characterized in that,
prior to the crystallization, the bromide content of
the magnesium chloride solution was reduced using
hydrogen peroxide.
The present invention is to be described below by an
exemplary embodiment.
Example:
An aqueous solution contained 67o by weight of
MgCl2 - 6 H20, 0 . 093 o by weight of bromide and 2 o by
weight of free HCl.
1000 g of this original solution were transferred in
each case into two 2000 cm3 glass beakers and to one
2000 cm3 flask.
The beakers were used to remove, after later addition
of hydrogen peroxide, the resultant. bromine by boiling
or stripping and by withdrawing it via suction feeding
it to suitable absorption.
The flask was used, after addition of hydrogen
peroxide, to remove the resultant bromine by applying
vacuum.
After adding 5 g each time of 35o strength by weight
aqueous hydrogen peroxide solution to each individual
solution, the experiments were started. The solutions
in the two glass beakers were heated to boiling or
stripped by injecting air at 4 1/min. The total volume

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of the solution was kept constant by adding ultrapure
water.
The third experiment was carried out by applying vacuum
(30 torr) to the flask.
Regardless of the removal method selected, in all three
experiments, bromide contents of < 25 ppm were found by
ion-chromatographic analysis.